Ho Chi Minh City (AsiaNews/Agencies) – Ho Chi Minh City authorities have decided to slaughter all poultry in the city to contain the spread the outbreak of the avian or bird flu that so far has killed 13 people in Vietnam. In the meantime, British experts have found that the gravity of the disease has been underestimated.

Starting tomorrow, Vietnam's largest city—Ho Chi Minh City (ex Saigon)—will kill all poultry within the city. Farms will be allowed only outside its boundaries.

"Once the outbreak has receded, we will allow farms to hatch eggs again, but poultry farming will be tightly controlled," said Bui Quang Anh, director of the Agriculture's Ministry's Animal Health Department.

Near the Mekong Delta, South Vietnam's former capital is home to 10 million people. Since late December 2004 it has been affected by the latest outbreak of bird flu.

It had already ordered the killing of all its ducks, which can carry the disease without showing symptoms of the virus, which kills 80 percent of the humans it infects. Now, it is the first city to order the total destruction of poultry.  Healthy birds would be frozen and eaten, while sick birds would be destroyed by burning or burial, Mr Anh said.

But poultry farming may never return to urban centres and measures to prevent another epidemic included raising birds in indoor farms safe from wild birds, Mr Anh said.

Migrating wildfowl, which can carry the H5N1 virus that can cross over to humans, are believed to have brought it to Asia.

Bui Quang Anh remains optimistic that the outbreak can be contained. He noted that no new human infection had been reported in the past week and all bird flu patients have been discharged. Still, he acknowledged that Vietnam is not yet in the clear.

Next week, the UN food agency and the World Organisation for Animal Health will hold a regional meeting in Ho Chi Minh City to discuss the emergency.

Since 2003, 45 people—32 Vietnamese, 12 Thais and one Cambodian—have died.

The spread of the deadly bird flu virus may have been underestimated because of a misunderstanding of how it affects the body, British scientists have said.

Oxford University experts studying deaths in Vietnam suggest the disease can attack all parts of the body, not just the lungs as had been first thought.

Their research revealed that a four-year-old boy had traces of the virus in his blood, nose and in the fluid around the brain.

For the lead researcher, Dr Menno de Jong, "[t]his illustrates that when someone is suffering from any severe illness we should consider if avian flu might be the cause."